1. Field of the Invention
Embodiments described herein relate generally to data storage units, systems and methods for storing a hibernation file in a hybrid disk drive.
2. Description of the Related Art
Hybrid hard disk drives (HDDs) include one or more rotating magnetic disks combined with non-volatile solid-state (e.g., flash) memory. Generally, a hybrid HDD has both the capacity of a conventional HDD and the ability to access data as quickly as a solid-state drive, and for this reason hybrid drives are expected to be commonly used in laptop computers. Some hybrid HDDs achieve the high performance of a solid-state drive by treating the non-volatile solid-state memory as a very large cache for the disk portion of the hybrid HDD. Specifically, all write data is typically accepted directly from the host into the flash memory portion of the hybrid HDD and, similarly, data read from the disk is written into flash as well. In this way, the flash memory can speed up write operations, since the relatively slower write-to-rotating disk operations do not affect how quickly data are accepted from the host unless the flash memory is full. Furthermore, the flash memory can speed up read operations by caching data that are more likely to be requested again by the host, i.e., the data used by the host most recently or most frequently. This minimizes the occurrence of relatively slow read-from-rotating-disk operations.
One issue common to laptop computers is the need to safely store a hibernation file as quickly as possible. This is because the read/write head and the spinning mechanism of the magnetic disk drive can be damaged when physical disturbances occur while data are written to the disk, such as when a user puts a laptop into the so-called “S4” or “hibernate” mode and then immediately closes and picks up the laptop. Ideally, a hybrid HDD is configured to store hibernation-file data to the flash memory portion of the drive, so that the read/write heads can be parked and the storage disks spun down immediately after hibernation mode is requested. Such a configuration of a hybrid HDD is problematic, however, because hibernation files can be quite large, requiring an undesirably large portion of the flash memory to be reserved, i.e., unused, to enable the storing of a hibernation file at all times during normal operation. So while such a hybrid HDD can be readily implemented, use of the available storage resources in the hybrid HDD would be inefficient and not cost effective.